What's your daily PH Swing?

kribbz · Apr 19, 2023

Looking through the APEX data I can say my daily swing is pretty consistent. What does everyone else's daily PH Swing look like?

NoohpyT · Apr 19, 2023

I usually have a .3 ph swing from 8ish to 8.3ish

Dburr1014 · Apr 19, 2023

.2ish

Randy Holmes-Farley · Apr 19, 2023

Just an FYI, the swing mostly reflects these factors:

1. Photosynthesis during the day consumes CO2 and raises pH.
2. Respiration 24/7 produces CO2 and lowers pH.
3. Changes in room CO2 can alter the pH, such as when a lot of people are around the tank with closed windows, or when windows go from open to closed, or cooking starts with a gas stove.
4, For a given amount of CO2 added or removed, the pH swing is larger at lower pH because the water is more strongly pH buffered at higher pH due to being closer to the carbonate/bicarbonate equivalent concentration point (pKa; about pH 8.92)
4, For a given amount of CO2 added or removed, the pH swing is larger at lower alkalinity because the water has more buffering bicarbonate and carbonate at higher alk.

Interestingly, there would be zero pH swing for reasons 1 and 2 if aeration was perfect. The pH swing is evidence that aeration is rarely perfect in reef tanks, despite people thinking they have lots of aeration.

Tuan’s Reef · Apr 19, 2023

Usually about .15 - .2 swing for me. Just swapped out my CO2 media yesterday and it shows.

kribbz · Apr 26, 2023

Randy Holmes-Farley said:
Just an FYI, the swing mostly reflects these factors:

1. Photosynthesis during the day consumes CO2 and raises pH.
2. Respiration 24/7 produces CO2 and lowers pH.
3. Changes in room CO2 can alter the pH, such as when a lot of people are around the tank with closed windows, or when windows go from open to closed, or cooking starts with a gas stove.
4, For a given amount of CO2 added or removed, the pH swing is larger at lower pH because the water is more strongly pH buffered at higher pH due to being closer to the carbonate/bicarbonate equivalent concentration point (pKa; about pH 8.92)
4, For a given amount of CO2 added or removed, the pH swing is larger at lower alkalinity because the water has more buffering bicarbonate and carbonate at higher alk.

Interestingly, there would be zero pH swing for reasons 1 and 2 if aeration was perfect. The pH swing is evidence that aeration is rarely perfect in reef tanks, despite people thinking they have lots of aeration.

Thanks for chiming in Randy, this is super insightful. I should have known better in making this post as the day I posted this my Apex DOS system went haywire and dumped 2843.7 mL's of alk into the tank and I came home to a snowstorm. It like saying "candyman," I spoke about how well things were going and the tank said "hold my beer and watch this!" So never say your tank is doing good!! hahaha

SO far I haven't lost anything. Alk jumped to about 12 dKh, pH jumped to almost 9 and ca dropped from 440 to 320. What I did was a small 5 gallon water change (75 gallon tank) and I used 3/8 diameter tubing to syphon as much of the precipitate off of the glass and rocks. I turned the skimmer up to wet skim and changed out several cups of milky white "Goo" as well as kept turkey basting the crap out of everything to keep the precipitate in the water column. This way I could keep changing the filter floss and removing as much of the "Snow" as I could. Everything looks good now and pH and Alk have come back to normal.

My question for all (if you have made it this far), I cannot get my CA to move. How do I get it back above 400? It hovers between 320-340 and I have more than doubled my Calc daily dosage. I currently dose Kalk at night and 2 part during the day. Previous to this mess, I dosed about 55 mL's of calc daily and I'm currently dosing about 125 mL's daily and I can only get it to jump to 340.

Randy Holmes-Farley · Apr 26, 2023

kribbz said:
My question for all (if you have made it this far), I cannot get my CA to move. How do I get it back above 400? It hovers between 320-340 and I have more than doubled my Calc daily dosage. I currently dose Kalk at night and 2 part during the day. Previous to this mess, I dosed about 55 mL's of calc daily and I'm currently dosing about 125 mL's daily and I can only get it to jump to 340.

I'd make a large, one time calculated correction to raise it, rather than adjusting the daily dose. Spread it out over a few days.

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